;; Contract: square : number -> number

;; Purpose: to computer the square of n

;; Example: (sqare 5)

;; Definition: [refines the header]
(define (square n)
  (* n n))

;; Tests:
(square 5)
;; expected value
25

(define (hypotenuse ln ht)
  (sqrt (+ (square ln)
           (square ht))))

(define a-big-number
  (+ (expt 2 100)   ;; 2^100
     (expt 3 100)   ;; 3^100
     (expt 5 100)   ;; 5^100
     (expt 7 100))) ;; 7^100

(+ 2
   (* 3 4))

(define (area-of-disk r)
  (* 22/7 (* r r)))

(define (area-of-ring outer inner)
  (- (area-of-disk outer)
     (area-of-disk inner)))

(area-of-ring 5 3)

(define (Fahrenheit->Celsius f)
  (* (- f 32)
     0.55))

(define (dollor->euro d)
  (* d 0.78))

(define (triangle l h)
  (/ (* l h)
     2))

(define (convert3 one two three)
  (+ one
     (* two 10)
     (* three 100)))

(define (f n)
  (+ (/ n 3)
     2))

(define (f210 n)
  (+ (sqr n)
     10))

(define (f220 n)
  (+ (* 1/2 (sqr n))
     20))

(define (21n n)
  (- 2 (/ 1 n)))

(define (wage h)
  (* 12 h))

(define (tax m)
  (* m 0.15))

(define (netpay h)
    (* h 12))

(define (sum-coins p n d q)
  (+ p (* n 5)
     (* d 10)
     (* q 25)))

(define (total-profit t p a)
  (- (* t 5)
     (* p 20)
     (* p .50)))

(define (somef x)
  (sin x x))